Synnefo » snf-nfdhcpd

#!/usr/bin/env python

#

# nfdcpd: A promiscuous, NFQUEUE-based DHCP server for virtual machine hosting

# Copyright (c) 2010 GRNET SA

#

#    This program is free software; you can redistribute it and/or modify

#    it under the terms of the GNU General Public License as published by

#    the Free Software Foundation; either version 2 of the License, or

#    (at your option) any later version.

#

#    This program is distributed in the hope that it will be useful,

#    but WITHOUT ANY WARRANTY; without even the implied warranty of

#    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

#    GNU General Public License for more details.

#

#    You should have received a copy of the GNU General Public License along

#    with this program; if not, write to the Free Software Foundation, Inc.,

#    51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.

#

import os

import re

import sys

import glob

import time

import logging

import logging.handlers

import threading

import traceback

import subprocess

import daemon

import daemon.pidlockfile

import nfqueue

import pyinotify

import IPy

import socket

from select import select

from socket import AF_INET, AF_INET6

from scapy.data import ETH_P_ALL

from scapy.packet import BasePacket

from scapy.layers.l2 import Ether

from scapy.layers.inet import IP, UDP

from scapy.layers.inet6 import IPv6, ICMPv6ND_RA, ICMPv6ND_NA, \

                               ICMPv6NDOptDstLLAddr, \

                               ICMPv6NDOptPrefixInfo, \

                               ICMPv6NDOptRDNSS

from scapy.layers.dhcp import BOOTP, DHCP

DEFAULT_CONFIG = "/etc/nfdhcpd/nfdhcpd.conf"

DEFAULT_PATH = "/var/run/ganeti-dhcpd"

DEFAULT_USER = "nobody"

DEFAULT_LEASE_LIFETIME = 604800 # 1 week

DEFAULT_LEASE_RENEWAL = 600  # 10 min

DEFAULT_RA_PERIOD = 300 # seconds

DHCP_DUMMY_SERVER_IP = "1.2.3.4"

LOG_FILENAME = "nfdhcpd.log"

SYSFS_NET = "/sys/class/net"

LOG_FORMAT = "%(asctime)-15s %(levelname)-6s %(message)s"

# Configuration file specification (see configobj documentation)

CONFIG_SPEC = """

[general]

pidfile = string()

datapath = string()

logdir = string()

user = string()

[dhcp]

enable_dhcp = boolean(default=True)

lease_lifetime = integer(min=0, max=4294967295)

lease_renewal = integer(min=0, max=4294967295)

server_ip = ip_addr()

dhcp_queue = integer(min=0, max=65535)

nameservers = ip_addr_list(family=4)

[ipv6]

enable_ipv6 = boolean(default=True)

ra_period = integer(min=1, max=4294967295)

rs_queue = integer(min=0, max=65535)

ns_queue = integer(min=0, max=65535)

nameservers = ip_addr_list(family=6)

"""

DHCPDISCOVER = 1

DHCPOFFER = 2

DHCPREQUEST = 3

DHCPDECLINE = 4

DHCPACK = 5

DHCPNAK = 6

DHCPRELEASE = 7

DHCPINFORM = 8

DHCP_TYPES = {

    DHCPDISCOVER: "DHCPDISCOVER",

    DHCPOFFER: "DHCPOFFER",

    DHCPREQUEST: "DHCPREQUEST",

    DHCPDECLINE: "DHCPDECLINE",

    DHCPACK: "DHCPACK",

    DHCPNAK: "DHCPNAK",

    DHCPRELEASE: "DHCPRELEASE",

    DHCPINFORM: "DHCPINFORM",

}

DHCP_REQRESP = {

    DHCPDISCOVER: DHCPOFFER,

    DHCPREQUEST: DHCPACK,

    DHCPINFORM: DHCPACK,

    }

def parse_routing_table(table="main", family=4):

    """ Parse the given routing table to get connected route, gateway and

    default device.

    """

    ipro = subprocess.Popen(["ip", "-%d" % family, "ro", "ls",

                             "table", table], stdout=subprocess.PIPE)

    routes = ipro.stdout.readlines()

    def_gw = None

    def_dev = None

    def_net = None

    for route in routes:

        match = re.match(r'^default.*via ([^\s]+).*dev ([^\s]+)', route)

        if match:

            def_gw, def_dev = match.groups()

            break

    for route in routes:

        # Find the least-specific connected route

        m = re.match("^([^\\s]+) dev %s" % def_dev, route)

        if not m:

            continue

        if family == 6 and m.group(1).startswith("fe80:"):

            # Skip link-local declarations in "main" table

            continue

        def_net = m.group(1)

        try:

            def_net = IPy.IP(def_net)

        except ValueError, e:

            logging.warn("Unable to parse default route entry %s: %s",

                         def_net, str(e))

    return Subnet(net=def_net, gw=def_gw, dev=def_dev)

def parse_binding_file(path):

    """ Read a client configuration from a tap file

    """

    try:

        iffile = open(path, 'r')

    except EnvironmentError, e:

        logging.warn("Unable to open binding file %s: %s", path, str(e))

        return None

    mac = None

    ips = None

    link = None

    hostname = None

    for line in iffile:

        if line.startswith("IP="):

            ip = line.strip().split("=")[1]

            ips = ip.split()

        elif line.startswith("MAC="):

            mac = line.strip().split("=")[1]

        elif line.startswith("LINK="):

            link = line.strip().split("=")[1]

        elif line.startswith("HOSTNAME="):

            hostname = line.strip().split("=")[1]

    return Client(mac=mac, ips=ips, link=link, hostname=hostname)

class ClientFileHandler(pyinotify.ProcessEvent):

    def __init__(self, server):

        pyinotify.ProcessEvent.__init__(self)

        self.server = server

    def process_IN_DELETE(self, event): # pylint: disable=C0103

        """ Delete file handler

        Currently this removes an interface from the watch list

        """

        self.server.remove_iface(event.name)

    def process_IN_CLOSE_WRITE(self, event): # pylint: disable=C0103

        """ Add file handler

        Currently this adds an interface to the watch list

        """

        self.server.add_iface(os.path.join(event.path, event.name))

class Client(object):

    def __init__(self, mac=None, ips=None, link=None, hostname=None):

        self.mac = mac

        self.ips = ips

        self.hostname = hostname

        self.link = link

        self.iface = None

    @property

    def ip(self):

        return self.ips[0]

    def is_valid(self):

        return self.mac is not None and self.ips is not None\

               and self.hostname is not None

class Subnet(object):

    def __init__(self, net=None, gw=None, dev=None):

        if isinstance(net, str):

            self.net = IPy.IP(net)

        else:

            self.net = net

        self.gw = gw

        self.dev = dev

    @property

    def netmask(self):

        """ Return the netmask in textual representation

        """

        return str(self.net.netmask())

    @property

    def broadcast(self):

        """ Return the broadcast address in textual representation

        """

        return str(self.net.broadcast())

    @property

    def prefix(self):

        """ Return the network as an IPy.IP

        """

        return self.net.net()

    @property

    def prefixlen(self):

        """ Return the prefix length as an integer

        """

        return self.net.prefixlen()

    @staticmethod

    def _make_eui64(net, mac):

        """ Compute an EUI-64 address from an EUI-48 (MAC) address

        """

        comp = mac.split(":")

        prefix = IPy.IP(net).net().strFullsize().split(":")[:4]

        eui64 = comp[:3] + ["ff", "fe"] + comp[3:]

        eui64[0] = "%02x" % (int(eui64[0], 16) ^ 0x02)

        for l in range(0, len(eui64), 2):

            prefix += ["".join(eui64[l:l+2])]

        return IPy.IP(":".join(prefix))

    def make_eui64(self, mac):

        """ Compute an EUI-64 address from an EUI-48 (MAC) address in this

        subnet.

        """

        return self._make_eui64(self.net, mac)

    def make_ll64(self, mac):

        """ Compute an IPv6 Link-local address from an EUI-48 (MAC) address

        """

        return self._make_eui64("fe80::", mac)

class VMNetProxy(object): # pylint: disable=R0902

    def __init__(self, data_path, dhcp_queue_num=None, # pylint: disable=R0913

                 rs_queue_num=None, ns_queue_num=None,

                 dhcp_lease_lifetime=DEFAULT_LEASE_LIFETIME,

                 dhcp_lease_renewal=DEFAULT_LEASE_RENEWAL,

                 dhcp_server_ip=DHCP_DUMMY_SERVER_IP, dhcp_nameservers=None,

                 ra_period=DEFAULT_RA_PERIOD, ipv6_nameservers=None):

        self.data_path = data_path

        self.lease_lifetime = dhcp_lease_lifetime

        self.lease_renewal = dhcp_lease_renewal

        self.dhcp_server_ip = dhcp_server_ip

        self.ra_period = ra_period

        if dhcp_nameservers is None:

            self.dhcp_nameserver = []

        else:

            self.dhcp_nameservers = dhcp_nameservers

        if ipv6_nameservers is None:

            self.ipv6_nameservers = []

        else:

            self.ipv6_nameservers = ipv6_nameservers

        self.ipv6_enabled = False

        self.clients = {}

        self.subnets = {}

        self.ifaces = {}

        self.v6nets = {}

        self.nfq = {}

        self.l2socket = socket.socket(socket.AF_PACKET,

                                      socket.SOCK_RAW, ETH_P_ALL)

        self.l2socket.setsockopt(socket.SOL_SOCKET, socket.SO_RCVBUF, 0)

        # Inotify setup

        self.wm = pyinotify.WatchManager()

        mask = pyinotify.EventsCodes.ALL_FLAGS["IN_DELETE"]

        mask |= pyinotify.EventsCodes.ALL_FLAGS["IN_CLOSE_WRITE"]

        inotify_handler = ClientFileHandler(self)

        self.notifier = pyinotify.Notifier(self.wm, inotify_handler)

        self.wm.add_watch(self.data_path, mask, rec=True)

        # NFQUEUE setup

        if dhcp_queue_num is not None:

            self._setup_nfqueue(dhcp_queue_num, AF_INET, self.dhcp_response)

        if rs_queue_num is not None:

            self._setup_nfqueue(rs_queue_num, AF_INET6, self.rs_response)

            self.ipv6_enabled = True

        if ns_queue_num is not None:

            self._setup_nfqueue(ns_queue_num, AF_INET6, self.ns_response)

            self.ipv6_enabled = True

    def _cleanup(self):

        """ Free all resources for a graceful exit

        """

        logging.info("Cleaning up")

        logging.debug("Closing netfilter queues")

        for q in self.nfq.values():

            q.close()

        logging.debug("Closing socket")

        self.l2socket.close()

        logging.debug("Stopping inotify watches")

        self.notifier.stop()

        logging.info("Cleanup finished")

    def _setup_nfqueue(self, queue_num, family, callback):

        logging.debug("Setting up NFQUEUE for queue %d, AF %s",

                      queue_num, family)

        q = nfqueue.queue()

        q.set_callback(callback)

        q.fast_open(queue_num, family)

        q.set_queue_maxlen(5000)

        # This is mandatory for the queue to operate

        q.set_mode(nfqueue.NFQNL_COPY_PACKET)

        self.nfq[q.get_fd()] = q

    def sendp(self, data, iface):

        """ Send a raw packet using a layer-2 socket

        """

        if isinstance(data, BasePacket):

            data = str(data)

        self.l2socket.bind((iface, ETH_P_ALL))

        count = self.l2socket.send(data)

        ldata = len(data)

        if count != ldata:

            logging.warn("Truncated send on %s (%d/%d bytes sent)",

                         iface, count, ldata)

    def build_config(self):

        self.clients.clear()

        self.subnets.clear()

        for path in glob.glob(os.path.join(self.data_path, "*")):

            self.add_iface(path)

    def get_ifindex(self, iface):

        """ Get the interface index from sysfs

        """

        path = os.path.abspath(os.path.join(SYSFS_NET, iface, "ifindex"))

        if not path.startswith(SYSFS_NET):

            return None

        ifindex = None

        try:

            f = open(path, 'r')

        except EnvironmentError:

            logging.debug("%s is probably down, removing", iface)

            self.remove_iface(iface)

            return ifindex

        try:

            ifindex = f.readline().strip()

            try:

                ifindex = int(ifindex)

            except ValueError, e:

                logging.warn("Failed to get ifindex for %s, cannot parse sysfs"

                             " output '%s'", iface, ifindex)

        except EnvironmentError, e:

            logging.warn("Error reading %s's ifindex from sysfs: %s",

                         iface, str(e))

            self.remove_iface(iface)

        finally:

            f.close()

        return ifindex

    def get_iface_hw_addr(self, iface):

        """ Get the interface hardware address from sysfs

        """

        path = os.path.abspath(os.path.join(SYSFS_NET, iface, "address"))

        if not path.startswith(SYSFS_NET):

            return None

        addr = None

        try:

            f = open(path, 'r')

        except EnvironmentError:

            logging.debug("%s is probably down, removing", iface)

            self.remove_iface(iface)

            return addr

        try:

            addr = f.readline().strip()

        except EnvironmentError, e:

            logging.warn("Failed to read hw address for %s from sysfs: %s",

                         iface, str(e))

        finally:

            f.close()

        return addr

    def add_iface(self, path):

        """ Add an interface to monitor

        """

        iface = os.path.basename(path)

        logging.debug("Updating configuration for %s", iface)

        binding = parse_binding_file(path)

        if binding is None:

            return

        ifindex = self.get_ifindex(iface)

        if ifindex is None:

            logging.warn("Stale configuration for %s found", iface)

        else:

            if binding.is_valid():

                binding.iface = iface

                self.clients[binding.mac] = binding

                self.subnets[binding.link] = parse_routing_table(binding.link)

                logging.debug("Added client %s on %s", binding.hostname, iface)

                self.ifaces[ifindex] = iface

                self.v6nets[iface] = parse_routing_table(binding.link, 6)

    def remove_iface(self, iface):

        """ Cleanup clients on a removed interface

        """

        if iface in self.v6nets:

            del self.v6nets[iface]

        for mac in self.clients.keys():

            if self.clients[mac].iface == iface:

                del self.clients[mac]

        for ifindex in self.ifaces.keys():

            if self.ifaces[ifindex] == iface:

                del self.ifaces[ifindex]

        logging.debug("Removed interface %s", iface)

    def dhcp_response(self, i, payload): # pylint: disable=W0613,R0914

        """ Generate a reply to a BOOTP/DHCP request

        """

        indev = payload.get_indev()

        try:

            # Get the actual interface from the ifindex

            iface = self.ifaces[indev]

        except KeyError:

            # We don't know anything about this interface, so accept the packet

            # and return

            logging.debug("Ignoring DHCP request on unknown iface %d", indev)

            # We don't know what to do with this packet, so let the kernel

            # handle it

            payload.set_verdict(nfqueue.NF_ACCEPT)

            return

        # Decode the response - NFQUEUE relays IP packets

        pkt = IP(payload.get_data())

        # Signal the kernel that it shouldn't further process the packet

        payload.set_verdict(nfqueue.NF_DROP)

        # Get the client MAC address

        resp = pkt.getlayer(BOOTP).copy()

        hlen = resp.hlen

        mac = resp.chaddr[:hlen].encode("hex")

        mac, _ = re.subn(r'([0-9a-fA-F]{2})', r'\1:', mac, hlen-1)

        # Server responses are always BOOTREPLYs

        resp.op = "BOOTREPLY"

        del resp.payload

        try:

            binding = self.clients[mac]

        except KeyError:

            logging.warn("Invalid client %s on %s", mac, iface)

            return

        if iface != binding.iface:

            logging.warn("Received spoofed DHCP request for %s from interface"

                         " %s instead of %s", mac, iface, binding.iface)

            return

        resp = Ether(dst=mac, src=self.get_iface_hw_addr(iface))/\

               IP(src=DHCP_DUMMY_SERVER_IP, dst=binding.ip)/\

               UDP(sport=pkt.dport, dport=pkt.sport)/resp

        subnet = self.subnets[binding.link]

        if not DHCP in pkt:

            logging.warn("Invalid request from %s on %s, no DHCP"

                         " payload found", binding.mac, iface)

            return

        dhcp_options = []

        requested_addr = binding.ip

        for opt in pkt[DHCP].options:

            if type(opt) is tuple and opt[0] == "message-type":

                req_type = opt[1]

            if type(opt) is tuple and opt[0] == "requested_addr":

                requested_addr = opt[1]

        logging.info("%s from %s on %s", DHCP_TYPES.get(req_type, "UNKNOWN"),

                     binding.mac, iface)

        if req_type == DHCPREQUEST and requested_addr != binding.ip:

            resp_type = DHCPNAK

            logging.info("Sending DHCPNAK to %s on %s: requested %s"

                         " instead of %s", binding.mac, iface, requested_addr,

                         binding.ip)

        elif req_type in (DHCPDISCOVER, DHCPREQUEST):

            resp_type = DHCP_REQRESP[req_type]

            resp.yiaddr = self.clients[mac].ip

            dhcp_options += [

                 ("hostname", binding.hostname),

                 ("domain", binding.hostname.split('.', 1)[-1]),

                 ("router", subnet.gw),

                 ("broadcast_address", str(subnet.broadcast)),

                 ("subnet_mask", str(subnet.netmask)),

                 ("renewal_time", self.lease_renewal),

                 ("lease_time", self.lease_lifetime),

            ]

            dhcp_options += [("name_server", x) for x in self.dhcp_nameservers]

        elif req_type == DHCPINFORM:

            resp_type = DHCP_REQRESP[req_type]

            dhcp_options += [

                 ("hostname", binding.hostname),

                 ("domain", binding.hostname.split('.', 1)[-1]),

            ]

            dhcp_options += [("name_server", x) for x in self.dhcp_nameservers]

        elif req_type == DHCPRELEASE:

            # Log and ignore

            logging.info("DHCPRELEASE from %s on %s", binding.mac, iface)

            return

        # Finally, always add the server identifier and end options

        dhcp_options += [

            ("message-type", resp_type),

            ("server_id", DHCP_DUMMY_SERVER_IP),

            "end"

        ]

        resp /= DHCP(options=dhcp_options)

        logging.info("%s to %s (%s) on %s", DHCP_TYPES[resp_type], mac,

                     binding.ip, iface)

        self.sendp(resp, iface)

    def rs_response(self, i, payload): # pylint: disable=W0613

        """ Generate a reply to a BOOTP/DHCP request

        """

        indev = payload.get_indev()

        try:

            # Get the actual interface from the ifindex

            iface = self.ifaces[indev]

        except KeyError:

            logging.debug("Ignoring router solicitation on"

                          " unknown interface %d", indev)

            # We don't know what to do with this packet, so let the kernel

            # handle it

            payload.set_verdict(nfqueue.NF_ACCEPT)

            return

        ifmac = self.get_iface_hw_addr(iface)

        subnet = self.v6nets[iface]

        ifll = subnet.make_ll64(ifmac)

        # Signal the kernel that it shouldn't further process the packet

        payload.set_verdict(nfqueue.NF_DROP)

        resp = Ether(src=self.get_iface_hw_addr(iface))/\

               IPv6(src=str(ifll))/ICMPv6ND_RA(routerlifetime=14400)/\

               ICMPv6NDOptPrefixInfo(prefix=str(subnet.prefix),

                                     prefixlen=subnet.prefixlen)

        if self.ipv6_nameservers:

            resp /= ICMPv6NDOptRDNSS(dns=self.ipv6_nameservers,

                                     lifetime=self.ra_period * 3)

        logging.info("RA on %s for %s", iface, subnet.net)

        self.sendp(resp, iface)

    def ns_response(self, i, payload): # pylint: disable=W0613

        """ Generate a reply to an ICMPv6 neighbor solicitation

        """

        indev = payload.get_indev()

        try:

            # Get the actual interface from the ifindex

            iface = self.ifaces[indev]

        except KeyError:

            logging.debug("Ignoring neighbour solicitation on"

                          " unknown interface %d", indev)

            # We don't know what to do with this packet, so let the kernel

            # handle it

            payload.set_verdict(nfqueue.NF_ACCEPT)

            return

        ifmac = self.get_iface_hw_addr(iface)

        subnet = self.v6nets[iface]

        ifll = subnet.make_ll64(ifmac)

        ns = IPv6(payload.get_data())

        if not (subnet.net.overlaps(ns.tgt) or str(ns.tgt) == str(ifll)):

            logging.debug("Received NS for a non-routable IP (%s)", ns.tgt)

            payload.set_verdict(nfqueue.NF_ACCEPT)

            return 1

        payload.set_verdict(nfqueue.NF_DROP)

        try:

            client_lladdr = ns.lladdr

        except AttributeError:

            return 1

        resp = Ether(src=ifmac, dst=client_lladdr)/\

               IPv6(src=str(ifll), dst=ns.src)/\

               ICMPv6ND_NA(R=1, O=0, S=1, tgt=ns.tgt)/\

               ICMPv6NDOptDstLLAddr(lladdr=ifmac)

        logging.info("NA on %s for %s", iface, ns.tgt)

        self.sendp(resp, iface)

        return 1

    def send_periodic_ra(self):

        # Use a separate thread as this may take a _long_ time with

        # many interfaces and we want to be responsive in the mean time

        threading.Thread(target=self._send_periodic_ra).start()

    def _send_periodic_ra(self):

        logging.debug("Sending out periodic RAs")

        start = time.time()

        i = 0

        for client in self.clients.values():

            iface = client.iface

            ifmac = self.get_iface_hw_addr(iface)

            if not ifmac:

                continue

            subnet = self.v6nets[iface]

            if subnet.net is None:

                logging.debug("Skipping periodic RA on interface %s,"

                              " as it is not IPv6-connected", iface)

                continue

            ifll = subnet.make_ll64(ifmac)

            resp = Ether(src=ifmac)/\

                   IPv6(src=str(ifll))/ICMPv6ND_RA(routerlifetime=14400)/\

                   ICMPv6NDOptPrefixInfo(prefix=str(subnet.prefix),

                                         prefixlen=subnet.prefixlen)

            if self.ipv6_nameservers:

                resp /= ICMPv6NDOptRDNSS(dns=self.ipv6_nameservers,

                                         lifetime=self.ra_period * 3)

            try:

                self.sendp(resp, iface)

            except socket.error, e:

                logging.warn("Periodic RA on %s failed: %s", iface, str(e))

            except Exception, e:

                logging.warn("Unkown error during periodic RA on %s: %s",

                             iface, str(e))

            i += 1

        logging.debug("Sent %d RAs in %.2f seconds", i, time.time() - start)

    def serve(self):

        """ Safely perform the main loop, freeing all resources upon exit

        """

        try:

            self._serve()

        finally:

            self._cleanup()

    def _serve(self):

        """ Loop forever, serving DHCP requests

        """

        self.build_config()

        # Yes, we are accessing _fd directly, but it's the only way to have a 

        # single select() loop ;-)

        iwfd = self.notifier._fd # pylint: disable=W0212

        start = time.time()

        if self.ipv6_enabled:

            timeout = self.ra_period

            self.send_periodic_ra()

        else:

            timeout = None

        while True:

            rlist, _, xlist = select(self.nfq.keys() + [iwfd], [], [], timeout)

            if xlist:

                logging.warn("Warning: Exception on %s",

                             ", ".join([ str(fd) for fd in xlist]))

            if rlist:

                if iwfd in rlist:

                # First check if there are any inotify (= configuration change)

                # events

                    self.notifier.read_events()

                    self.notifier.process_events()

                    rlist.remove(iwfd)

                for fd in rlist:

                    try:

                        self.nfq[fd].process_pending()

                    except RuntimeError, e:

                        logging.warn("Error processing fd %d: %s", fd, str(e))

                    except Exception, e:

                        logging.warn("Unknown error processing fd %d: %s",

                                     fd, str(e))

            if self.ipv6_enabled:

                # Calculate the new timeout

                timeout = self.ra_period - (time.time() - start)

                if timeout <= 0:

                    start = time.time()

                    self.send_periodic_ra()

                    timeout = self.ra_period - (time.time() - start)

if __name__ == "__main__":

    import capng

    import optparse

    from cStringIO import StringIO

    from pwd import getpwnam, getpwuid

    from configobj import ConfigObj, ConfigObjError, flatten_errors

    import validate

    validator = validate.Validator()

    def is_ip_list(value, family=4):

        try:

            family = int(family)

        except ValueError:

            raise validate.VdtParamError(family)

        if isinstance(value, (str, unicode)):

            value = [value]

        if not isinstance(value, list):

            raise validate.VdtTypeError(value)

        for entry in value:

            try:

                ip = IPy.IP(entry)

            except ValueError:

                raise validate.VdtValueError(entry)

            if ip.version() != family:

                raise validate.VdtValueError(entry)

        return value

    validator.functions["ip_addr_list"] = is_ip_list

    config_spec = StringIO(CONFIG_SPEC)

    parser = optparse.OptionParser()

    parser.add_option("-c", "--config", dest="config_file",

                      help="The location of the data files", metavar="FILE",

                      default=DEFAULT_CONFIG)

    parser.add_option("-d", "--debug", action="store_true", dest="debug",

                      help="Turn on debugging messages")

    parser.add_option("-f", "--foreground", action="store_false",

                      dest="daemonize", default=True,

                      help="Do not daemonize, stay in the foreground")

    opts, args = parser.parse_args()

    try:

        config = ConfigObj(opts.config_file, configspec=config_spec)

    except ConfigObjError, err:

        sys.stderr.write("Failed to parse config file %s: %s" %

                         (opts.config_file, str(err)))

        sys.exit(1)

    results = config.validate(validator)

    if results != True:

        logging.fatal("Configuration file validation failed! See errors below:")

        for (section_list, key, unused) in flatten_errors(config, results):

            if key is not None:

                logging.fatal(" '%s' in section '%s' failed validation",

                              key, ", ".join(section_list))

            else:

                logging.fatal(" Section '%s' is missing",

                              ", ".join(section_list))

        sys.exit(1)

    logger = logging.getLogger()

    if opts.debug:

        logger.setLevel(logging.DEBUG)

    else:

        logger.setLevel(logging.INFO)

    if opts.daemonize:

        logfile = os.path.join(config["general"]["logdir"], LOG_FILENAME)

        handler = logging.handlers.RotatingFileHandler(logfile,

                                                       maxBytes=2097152)

    else:

        handler = logging.StreamHandler()

    handler.setFormatter(logging.Formatter(LOG_FORMAT))

    logger.addHandler(handler)

    if opts.daemonize:

        pidfile = daemon.pidlockfile.TimeoutPIDLockFile

            config["general"]["pidfile"], 10)

        d = daemon.DaemonContext(pidfile=pidfile,

                                 stdout=handler.stream,

                                 stderr=handler.stream,

                                 files_preserve=[handler.stream])

        d.umask = 0022

        d.open()

    logging.info("Starting up")

    proxy_opts = {}

    if config["dhcp"].as_bool("enable_dhcp"):

        proxy_opts.update({

            "dhcp_queue_num": config["dhcp"].as_int("dhcp_queue"),

            "dhcp_lease_lifetime": config["dhcp"].as_int("lease_lifetime"),

            "dhcp_lease_renewal": config["dhcp"].as_int("lease_renewal"),

            "dhcp_server_ip": config["dhcp"]["server_ip"],

            "dhcp_nameservers": config["dhcp"]["nameservers"],

        })

    if config["ipv6"].as_bool("enable_ipv6"):

        proxy_opts.update({

            "rs_queue_num": config["ipv6"].as_int("rs_queue"),

            "ns_queue_num": config["ipv6"].as_int("ns_queue"),

            "ra_period": config["ipv6"].as_int("ra_period"),

            "ipv6_nameservers": config["ipv6"]["nameservers"],

        })

    # pylint: disable=W0142

    proxy = VMNetProxy(data_path=config["general"]["datapath"], **proxy_opts)

    # Drop all capabilities except CAP_NET_RAW and change uid

    try:

        uid = getpwuid(config["general"].as_int("user"))

    except ValueError:

        uid = getpwnam(config["general"]["user"])

    logging.debug("Setting capabilities and changing uid")

    logging.debug("User: %s, uid: %d, gid: %d",

                  config["general"]["user"], uid.pw_uid, uid.pw_gid)

    # Keep only the capabilities we need

    # CAP_NET_ADMIN: we need to send nfqueue packet verdicts to a netlinkgroup

    capng.capng_clear(capng.CAPNG_SELECT_BOTH)

    capng.capng_update(capng.CAPNG_ADD,

                       capng.CAPNG_EFFECTIVE|capng.CAPNG_PERMITTED,

                       capng.CAP_NET_ADMIN)

    capng.capng_change_id(uid.pw_uid, uid.pw_gid,

                          capng.CAPNG_DROP_SUPP_GRP|capng.CAPNG_CLEAR_BOUNDING)

    logging.info("Ready to serve requests")

    try:

        proxy.serve()

    except Exception:

        if opts.daemonize:

            exc = "".join(traceback.format_exception(*sys.exc_info()))

            logging.critical(exc)

        raise

# vim: set ts=4 sts=4 sw=4 et :